4 ms·

Here I thought a kilogram was defined by water... oh well, looks like that definition is slightly outdated. https://en.wikipedia.org/wiki/Litre#Rough_conversio

• fredley 11y ago
  The used to be defined as one kg of water, but it is not an official SI unit (it is part of the SI accepted metric system, which does not require such rigorous definitions).
  • masklinn 11y ago
    The litre is defined as 1dm^3, the mass-based definition was dropped in '64.
  • jacquesm 11y ago
    > The used to be defined as one kg of water I think you meant 'one litre'
    • rangibaby 11y ago
      One kg and one litre of water are the same thing.
      • jacquesm 11y ago
        At what temperature?
        • protomyth 11y ago
          "water at the melting point of ice" from an old definition
          • jacquesm 11y ago
            Exactly, so you need to add that or it won't be true most of the time.
      • kqr 11y ago
        Inofficially, it has been. Technically, it's not quite true. Water has a density of 999.97 kg/m³.
        • seunosewa 11y ago
          That's unfortunate. How did it come to be that way?
          • lvh 11y ago
            Water is too hard to keep constant, and too hard to reproduce. Keeping it exactly in 1dm3 is tricky, for example. Not for "regular" use, with a few significant digits of course; but when you're defining fundamental physical constants, atoms count.
      • ColinWright 11y ago
        That depends on the temperature ...
      • nkrisc 11y ago
        At 0C
      • ufo 11y ago
        Not really. Because of temperature, usitipe composition, etc, the weight of a liter of water is not precise enough for physicists.
    • mdellabitta 11y ago
      One kg of water is definitely one kg.